JTAG asks the chip
You will learn
How a cable finds the chip on a board and reads its IDCODE.
JTAG is the cable protocol for talking to the chip on a board. Before programming, the tool shifts out the IDCODE of every device on the chain. This recording decodes the codes our bench answers with, and shows what an even code means: no IDCODE at all. Compare it with the decoder from lesson 2.
Try it
Find which IDCODE belongs to an XC7A200T and which to an XC7A100T.
All lessons
Module 1 · The chip
What an FPGA is, which chip we use, and how its pins meet the board.
Module 2 · Numbers in hardware
Bits, trits and number formats, and what arithmetic costs in logic.
Module 3 · Your t27 program
Write a spec, test it, and see why compiling is not the same as being right.
Module 4 · Inside t27c
How the compiler reads a spec and what it writes, including the native t27b.
Module 5 · From spec to hardware
The Verilog t27c writes, the cells it becomes, and what one LUT does.
Module 6 · Reading synthesis
What yosys reports about your design, and which warnings matter.
Module 7 · Place, route, timing
Where the cells land on the die, and whether the clock is met.
Module 8 · The bitstream
How a routed design becomes the bits the chip loads, with no Vivado.
Module 9 · On the board
Ask the chip who it is, load the bits, and check them.
Module 10 · Lab: our own research
A number format of our own, an honest scoreboard, and a model's tables multiplied on the board.